We develop an analytical model to describe sub-bandgap optical absorption in two-dimensional semiconducting transition metal dichalcogenide (s-TMD) nanoflakes. The material system represents an array of few-layer molybdenum disulfide crystals, randomly orientated in a polymer matrix. We propose that optical absorption involves direct transitions between electronic edge-states and bulk-bands, depends strongly on the carrier population, and is saturable with sufficient fluence. For excitation energies above half the bandgap, the excess energy is absorbed by the edge-state electrons, elevating their effective temperature. Our analytical expressions for the linear and nonlinear absorption could prove useful tools in the design of practical photonic devices based on s-TMDs.
@article{arxiv.1602.06298,
title = {Theory of edge-state optical absorption in two-dimensional transition metal dichalcogenide flakes},
author = {Maxim Trushin and Edmund J. R. Kelleher and Tawfique Hasan},
journal= {arXiv preprint arXiv:1602.06298},
year = {2016}
}